The present application is directed to the separation of components found in whole blood, and more particularly to the separation and extraction of platelets from other blood components such as red blood cells (erythrocytes) and white blood cells (leukocytes).
Platelets, while not considered real cells, are essential for certain biological operations such as blood clotting in a process called “hemostasis” (i.e. the stopping of bleeding) and are also a natural source of growth factors (which stimulate cell growth). Patients with certain diseases, such as AIDS and patients undergoing medical procedures including chemotherapy, bone marrow transplants, stem cell treatments, organ transplants and orthopedic procedures, among others often require regular and repeated transfusions of platelets.
For example, platelet-rich plasma (PRP) is often used in medical procedures where growth factors promote wound healing. One particularly interesting emerging application is in orthopedics, where patients who have undergone surgeries such as knee or hip replacements generally benefit from PRP obtained from whole blood. It is also considered beneficial to use platelets from a patient's own blood as this is understood to minimize immune response.
Collected whole blood is generally separated into components by one of three methods. A centrifuge can be used in a “soft spin” (˜200×G) which separates whole blood into plasma (including platelets and white blood cells) and red blood cells or in a “hard spin” (greater than 200×G) which further separates the white blood cells from the platelets, in addition to the separation of the red blood cells. The third method is sedimentation where the blood simply sits for an extended period time until the red blood cells and plasma are separated by gravity. Still another described method of blood separation involves absorption of the blood component onto beads coated with an absorbent material. Wherein the coating is selected to absorb a particular type of component.
A well-known blood separation technique called aphaeresis employs centrifuge operations, and includes taking blood from a donor or patient, passing the blood through an apparatus that separates out desired components and returns the remainder of the blood to circulation. These centrifuge operations separate out the components based on component density. It is known that red-blood cells have the highest density, then white blood cells, and finally platelets. Therefore, depending on how many different components of the blood are needed, the blood will be subjected to various intervals of centrifugal steps, i.e., the “soft spin” and/or “hard spin”. In addition, some devices use density gradient to help the separation and ensure separated layers stay apart. If enrichment (concentration) of platelets is desired, a porous barrier is further used to allow the passage of plasma but retains platelets. Most of these aphaeresis/platelet separation machines and other blood separation machines are generally bulky and often require a dedicated facility and operator which then requires a donor to visit the facility.
It is therefore considered beneficial to have a smaller, simpler device where blood can be drawn and the separation performed at the same location, without having to go through the procedure of being sent to a central lab, logged and placed in a queue for separation. Such a device could also potentially provide cost-savings, as longer single-use disposable tubing is employed to line large centrifuge based systems. Another advantage of a small portable separation device is minimal cross contamination, since different patients do not share the same instrument, just like disposable syringes.